hetmann



April 13, 1954 R. HETMANN PISTON PUMP FOR DE Filed March 22, 1952 Patented Apr. 13, 1954 UNITED sTATEs PISTON r PUMP- FOR' DELIVERINGLLUBRICAT- .ING i OIL .tIN LINTERNAL-COMBUSTION EN =.GINES Richard Hetmann,

6 Claims. l

This invention relates to improvements inoil :pumps for internal combustion engines-and more particularly to a piston typepump fordelivering "the-lubricating oil to tlie parts to be lubricated tint .anfl'mternal combustion engine.

:Imknown constructions of internal combustion rienginesprovided with an oilipump of a piston type, it has ;been.necessary to provide spaced suction andrpressure valves toicontrol the oil cadmission anddischargazand, in someconstrucrtions, also provide such valves'in thepiston. In such constructions the machining and boring for :valves and valve seats involve considerable trouble, andexpense :and this is more particular- :lytrue, when the, pump ,cylinderszare bored in ;;.the casing 01' crankcase of the. internal combus- ,tion engine. i111 additionto the foregoing, the usual oil supply systemslfor internal combustion engines are providedwith-apressure relief valve which is set so that, a predetermined pressure is not exceeded :by theroilrpump.

Ehe primary object of rthezpresent invention is to provide animproved pistonlpump construction, which is relatively simple to make and which includes relatively ,few parts.

A further object of the inventionis to-provide apiston pump construction, in which it,is;unnecessary to; machine and bore ,Lthe cylinderof the pump toprovide for valves and ivalve -seats.

Alfurther object offlthe invention isto provide pressure, and which 1 includes relatively few simple parts.

In a preferred construction, the improved piston, pump, according to the invention, comprises two opposing pistons mounted in facing relationship in a cylindrical pumpchamber which,

may be made by boring a partrof'the crankcase of the engine. Means lSiDI'OVidGdfOI, actuating uoneof thesepistons by the engine, whereasthe .other, piston is provided as aivalvecpiston having a; suction valve adaptedtoppen .andtpermitisthe v Stuttgart Bad Cannstatt, ,Germany, assignor to Dr. Ing. H. C. F. Porsche K.G.,- Stuttgart-Zuffenhausen, Germany Application; Ma110h122, 1952,: Serial No. 278,002

Claimsfpriority, application: Germany April 21," 1951 flow of oilinto the cylinder lwhen theJpump-pistennis actuated away from-the valve piston in the chamber. iromsthe pump is arrangedin the chamber: wall In this construction, the oil outlet intermediate its endstso that oil drawn into the chamber on the suction'stroke of the pumping pump chamber and .the .head.1of"which is pro vided with a suction .valve :normally. closed by :a spring arranged in;tl1e hollow piston. The; valve piston is .biased ,towardithe .pump' piston ;Lby

, means of: a spring selecteditoprovidevthermaximum desired pressurein the lubricating system and is arrangedto have a definitelengthof stroke, in the forward direction so 1 that its piston .head portionoisiadapted to cover theooil outlet from the, pump chamber :during the 1 suction stroke of the :pump :piston.

The pump chamber is preferably anopen- .ended .cylinderof uniform inside diameter.

the improved piston pump of thepresentminmention and the improved lubricating oil system foiainternal combustion engines; provided there- ;byincludesother features, objects, and advan- :tages described more in ,detail hereinafter in connection with theaccompanyingdrawing,illusfl .trating one embodiment of the invention.

In-the drawing the single figure is a broken longitudinal-sectional view through a portion of an engine showing apiston pump constructed anctarranged according to the invention.

Referring to the drawing, in which thevpump is arranged vertically in the, crankcase of an internal combustion enginebelow the crankshaft thereof, a projection i comprising-an integral part of-the wallof the casing 2 of the engine is provided witha cylindrical bore 3 formingthe pump cylinder and chamber The bore 3 is preferablymade of uniform diameter throughout its length to simplify construction and :accommm ,idatesuapump piston iend avalvepiston 5 slidable therein. The pump piston 4 comprises. a

part in addition to that which reciprccates in cylinderi3 including an intermediate portionfi of reduced diameter, the upper shoulder .formecl thereby being engaged by a flanged. plate 11 :held

against theshoulder ..by a spring 8 surrounding the pistonJ4 and-resting on theupper surfaceioi the projection l. ,The spring-dis.mountedzunder acompression and. biases the t-pistonxll cupwardly against a cam 9, provided, for example, on a crankshaft ID of the internal combustion engine. The upper part of the pump piston 4 extends through a bore I l in a projection l2 integral with the casing 2 of the engine. The bore II in the projection l2 serves to guide the pump piston 4 and maintain it in proper alignment when acted upon by the cam 9. The bore II is preferably of the same diameter as the cylindrical bore 3 and may be made at the same time and with the same tools as those used for making and machining the bore 3.

The valve piston 5, the head of which is located in the lower portion of the pump cylinder 3 is provided with a longitudinal stepped bore IS, the smaller upper end of which is in the piston head and closed by means of a valve disc l4 resting on the head of the valve piston 5. The valve disc I4 is normally maintained on its seat by a compression spring l5 mounted in the larger portion of the bore I3 and seated in a flanged plate I5 supported by a pin 13 connected to the valve disc M. The spring i5 is under compression and need be only of sufficient strength to seat the valve disc l4 while at the same time permitting the valve disc to be unseated when suction is supplied thereabove.

The lower end ofthe valve piston 5 is provided with an annular flanged plate It, the inner rim of which advantageously rests in a shouldered recess adjacent the lower end of the valve piston 5. The flange of the plate it extends downwardly for retaining a spring ll mounted under compression between the plate l6 and a cover id for the crankcasing 2. The cover 18 serves to close the bottom of the casing 2 below the pump and is provided with an oil drainage plug it. The plate I6 is set on the valve piston 5 at the propel distance from the top of the piston so that the upper surface of the plate it; engages the lower surface of the block or projection i when the upper portion of the piston 5 extends above and covers the oil outlet 20 for the pump chamber. In this position of the valve piston, its upper end is located at the position of the dotand-dash line 14.

In the operation of the pump, it may be assumed that the engine oil in the crankcase extends to a level somewhat above the projection I, possibly up to the projection 12, so that oil surrounds the pump and is available inside the valve piston 5 as soon as the crankshaft it commences to rotate. The drawing illustrates the position of the piston 4 in its lower dead center position with oil being forced through the outlet 25. As the oil flows out of the pump chamber the piston 5 moves up under the action of the spring I! until, under normal conditions, it engages the lower end of the piston 4.

During the. upward stroke of the pump piston 4, under the action of the spring 8, the valve piston 5 follows along until the plate 16 engages the lower surface of the block corresponding to the position of the dot-and-dash line l4, and the pump piston 4 continues on to a higher point or until its lower end reaches the position of the dot-and-dash line 4'. As the piston 4 leaves the piston 5 it applies suction in the cylinder 3, lifts the valve disc i l and causes the flow of oil into the pump cylinder 3 between the pistons. When the piston is at its top dead center position, a space or volume [9 is provided in cylinder 3 which is under a reduced pressure and filled with oil drawn in from that surrounding the pump. This oil flows in through 4 the bore l3, around the disc I and into the space l9, it being noted that during this operation, the valve piston 5 eifectively covers and seals off the outlet 20, so that the oil pressure is maintained in the oil lines of the engine during the suction stroke of the pump.

During the downward movement of the pump piston 4, under the action of the cam 9, the pressure on the oil between the pistons in space I9 is increased because of the sealing of the disc I4 and power of the spring I1. The piston 5 is therefore forced downwardly until the outlet 20 is uncovered, permitting the oil from cylinder 3 to flow thereinto. The drawing shows the position of the parts of the pump at this stage of the operation.

The oil delivered by the pump through the outlet 20 is distributed through ducts 2!, 22, and 23 to the various bearings and other parts of the internal combustion engine to be lubricated, and lubricating oil is delivered to these lines under the pump pressure as long as the engine is, running. When the engine is stopped, the pump maintains a perfect seal against the reverse flow of oil through the line 20, regardless of the position of the piston 4. Therefore, the built-up oil pressure will cause flow of oil through the bearings and parts of the engine to be lubricated after the engine stops running.

If some trouble should develop in the engine which would result in a pressure increase in the oil lines 20 to 23, for instance the stoppage of one of these lines, the pump would not increase the pressure above the normal maximum pressure for which the pump is made and controlled by the power of the spring l1. Furthermore, the pump will deliver only the amount of oil used by the operative parts of the lubricating system under such conditions and, if no oil is permitted to flow through the outlet 20, the pump will automatically cease delivering oil when the maximum pressure is reached even though the pistons continue to reciprocate. Therefore, the pump and lubricating system of the present invention requires no pressure relief valve.

In the circumstance referred to above where the pressure in the outlet 20 is at the maximum set pressure, the downward movement of the pump piston 4 will not cause the flow Of oil into the outlet 20 but the volume of oil between the pistons 4 and 5 will remain approximately the same and the piston 5 will merely be forced down to a greater extent, than under normal operation, to accommodate the volume of oil held between the piston at the maximum pressure in the system. While the pump is operating under such conditions, there will be no reduction of pressure between the pistons during the up stroke and the valve It will not be opened to draw in additional oil from the space surrounding the pump. The pump, therefore, continues to work under no-load conditions, and only when the pressure in the pipe 29 falls below the maximum set pressure of the spring I! will the pump begin to deliver oil. A pump constructed and arranged according to the invention, therefore, has the advantage that no pressure is developed in the oil system above the predetermined set maximum, which could damage the pump or the piping system of the engine.

The improved piston pump of the present invention is particularly useful in the lubricating systems of internal combustionengines wherein the pump piston is actuated by the engine, but it may have a corresponding advantage in other systems where it is desired to pump a fluid and operate the system at a predetermined maximum pressure or at some lower pressure. While the pump described and illustrated in connection with the present invention is operated by a cam to force the piston in one direction, it is apparent that a cam may be used which would eiiect positive actuation of the pump piston in both directions, or that other driving means coupled to the engine could be employed for reciprocating the pump piston in either or both directions.

What is claimed as new is:

l. A piston pump for the delivery of lubricating oil to the parts of an internal combustion engine to be lubricated, comprising a pump cylinder, a pump piston in said cylinder, means operatively associated with the engine for Operating said piston, said cylinder being provided with an oil outlet opening through the side wall of the cylinder intermediate its ends, a second piston in said cylinder having the same diameter as and facing said pump piston, said pistons being operable on a common in the pump cylinder, means for biasing said second piston toward the pump piston, and means including a non-return valve for admitting oil into said cylinder between said pistons.

2. A piston pump for internal combustion engines as claimed in claim 1 in which said second piston is biased toward the pump piston by means of a spring having a power adapted to provide not more than a predetermined maximum pres-- sure in the pump cylinder.

3. A piston pump as claimed in claim 1 in which said second. piston is provided with an axial passageway therethrough for admitting oil into the pump cylinder between the pistons, said valve for admitting oil being located in a position to control the passageway through said 0nd piston and being adapted to prevent the flow of oil from the cylinder through said passageway.

4. A piston pump as claimed in claim 1, including means for limiting the forward movement of the second piston to a position in the pump cylinder at which the side wall of the second piston just covers the oil outlet in the side wall of the pump cylinder.

5. In an internal combustion engine including a crankcase and a crankshaft therein, a piston pump for the delivery of lubricating oil to the parts of the internal combustion engine to be lubricated, said pump including a cylinder located in the portion of the crankcase normally containing a body of lubricating oil, a reciprocable piston in said cylinder, means operated by the crankshaft for moving said piston in at least one direction in said cylinder, said cylinder being provided with an oil outlet opening through the side wall of the cylinder intermediate its ends, means for conducting oil from said outlet to the parts of the engine to be lubricated, a valve piston in said cylinder having the same diameter as and facing said pump piston, spring means for biasing said valve piston toward the pump piston, said valve piston having a passageway therethrough for the flow of oil into the cylinder between the said pistons, a suction valve for said passageway adapted to prevent the flow of oil from the cylinder through said passageway, and means for limiting the forward movement of said valve piston in the cylinder to a position just beyond where the side wall of the valve piston covers the oil outlet in the side wall of the pump cylinder.

6. An internal combustion engine and a piston pump therefor as claimed in claim 5 in which the crank case of the engine includes a block-like portion located in the portion of the crank case normally containing a body of lubricating oil, said pump cylinder being located in said block and having open ends on opposite sides of the block into which the pump piston and the valve piston extend respectively, said block constituting at least in part the means for limiting the forward movement of the valve piston, and means carried b the valve piston for engaging said block when the forward end of the valve piston has moved to a position to cover the oil outlet in the side wall of the pump cylinder.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,456,461 Page May 22, 1923 1,688,978 McCallum Oct. 23, 1928 1,911,474 Smith May 30, 1933 2,257,707 Sladky Sept. 30, 1941 2,504,499 Cloud Apr. 13, 1950 

